I use GParted on a live CD/ISO for similar situations. I personally have never put my home directory on a separate partition, so I don’t know if this would somehow not work for you and I suggest backing up your data!

I think the weakest computer I’ve had Linux on was an original Xbox running DSL.

Go into the game’s settings in Steam and then set its compatibility to Proton Hotfix. You should then have the option to install it.

I would hate snaps a lot less if Ubuntu just stopped trying to force me to use them.